Helium escape valves are present in some dive watches for evacuating helium that has penetrated the watch case during saturation dives where divers inhale a gas mixture containing helium and oxygen. This allows them to stay inside a diving bell or underwater habitat for several days. During this time period, helium may penetrate the watch. In the absence of such a valve, the excess internal pressure caused by helium that has seeped in may, during the decompression phase, cause damage to the watch, such as, for example, loss of the crystal which may pop out or break.
There are manual and automatic helium escape valves. Manual valves operate simply by tightening a sealing element, such as a head, onto the case middle, in the same manner as a screw-in crown. Manual valves have the drawback that the watch is not water-resistant if the valve is not tightened up again. Automatic valves are activated automatically, as their name indicates, when the difference in pressure between the inside of the watch case and the external environment reaches a critical threshold.
A first type of automatic valve is one that the user cannot block, the principles of which are described in Swiss Patent No CH491246. This valve, which, in most cases, is mounted flush with the case middle, takes the form of a simple valve limiting the pressure inside the watch case.
The drawback of this type of valve is that it opens automatically with no possibility of stopping gas escaping and therefore of fluid entering the watch, which is problematic when decompression is performed in a humid environment.